Wild insects are more important than domesticated honey bees for boosting crop yields, a study in Science suggests.

Farmers often bring honey bee colonies to their fields to pollinate crop plants. But wild pollinating insects, such as bumblebees and butterflies, also can improve yields. Since wild pollinators are on the decline, the study authors wanted to find out how big a role these bugs played in crop growth.

The team studied 600 fields covering 41 crop systems in North America, South America, Europe, Asia, Africa, and Australia. The farms grew everything from coffee to watermelons and had varying levels of honey bees and wild insects. The researchers measured how often the bugs visited flowers, the amount of pollen deposited, and “fruit set,” or the development of flowers into mature seeds or fruit.

Wild insects increased fruit set in every crop system, while honey bees did so in 14 percent of the systems, the team found. And visits from wild insects increased fruit set twice as much as visits from honey bees.

The researchers saw a benefit from wild pollinators even if a field was well-stocked with honey bees. That result suggests that “managed honey bees supplement the pollination service of wild insects, but cannot replace it,” the authors write. To maintain this valuable service, farmers will need to adopt wildlife-friendly practices such as restoring patches of natural landscape in their fields. — Roberta Kwok | 28 February 2013